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One of Dzhokhar's friends says he "was the last person you'd expect to do this"

Dzhokhar Tsarnaev's Twitter account and VK Russian social networking profile have drawn heavy public scrutiny, but he left another, more hidden social media trail: a deleted Instagram account that sources close to him tell CNN once belonged to the accused Boston bomber.

The Instagram account, with the user name "jmaister1," no longer exists, and friends of Tsarnaev's say it was deleted only recently. An Instagram spokesman declined to comment on the account or disclose when the account was deleted.

CNN National Security Analyst Juliette Kayyem says the account could be significant.

"If I were an investigator right now, obviously the platform he deleted matters the most," she said.

Traces of the jmaister1 account were still visible this week in Google's Web cache and on other archiving sites. Digital sleuths often use those tools to find glimpses of deleted material.

"It's exactly like an archive," tech entrepreneur and programmer Sam Altman explained. "So no matter what changes were made to the page today, on the current server, Google has this sort of imprint from a couple of weeks ago."

Tsarnaev's complete account could not be recovered with those tools. Google's cache stores the pages it indexes for variable lengths of time: sometimes days, sometimes weeks.

The digital traces that remain show that Tsarnaev added a "like" on several photos referring to Chechnya that were posted by other Instagram users. One shows Chechen warlord Shamil Basayev, a onetime government official who later masterminded terrorist attacks against Russia. Basayev was killed in 2006.

This image from the site Statigram shows an image that Dzhokhar Tsarnaev "liked" of warlord Shamil Basayev.

Another pro-Chechnya image that Tsarnaev "liked" carries a string of hashtags including #FreeChechenia #Jihad #Jannah #ALLAH #Jesus and #God. An academic Chechnya expert whom CNN consulted said the images illustrated a familiarity with Chechen politics and iconography.

Tsarnaev's Instagram account wasn't widely known; CNN spoke with several friends of his who said they were unaware of its existence. Two of his high-school classmates, however, spoke about the account and said he used it to keep in touch with a close-knit group of school friends.

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The two classmates say they are shocked by -- and in some cases skeptical of -- the charges being levied at the friend they knew as "Jahar." As one said, "Jahar was the last person you'd expect to do this. I've honestly never heard anybody say anything bad about him."

Since Tsarnaev's account was deleted, little of what he wrote and posted remains publicly visible, but Kayyem expects investigators to take a closer look at whatever data they can reconstruct.

"Were there clues embedded in the combination of images that can tell us something about what Dzhokhar was thinking?" she asked. "Some of those pictures are very benign. Some of them standing alone don't mean anything."

Instagram makes clear in its terms of service that it will turn its records over to law enforcement officials when it receives a valid subpoena or search warrant.

"Given the volume of real-time content on Instagram, some information may only be stored for a short period of time," Instagram says on its site. "We do not retain data for law enforcement purposes unless we receive a valid preservation request."